Why doesn't Absinthe expose Plug.Conn?

Absinthe.Plug has this, Absinthe does not. Absinthe will continue to insist that GraphQL operations are handled without regard for transport. Absinthe.Plug is welcome to map Plug.Conn data to the context and map context info back to the conn, and I’m happy to consider proposals that make that more streamlined.

If you mean Absinthe middleware here, consider just ditching a resolver for that operation and just using middleware. resolve is a thin layer around middleware anyway.